Agent: Paul D. Yasger Abbott Laboratories20080161293 - Antitumor agent: h20080161294 - Urea derivative, medicinal composition containing the same, and medicinal use of these: In the formula, R1 represents a hydrogen atom or a C1-6 alkyl group which may have a substituent, R2 is a hydrogen atom or a C1-6 alkyl group, R3 is a hydrogen atom, a C1-6 alkyl group or the like, R4, R5 and R6 are independe